ABSTRACT Support is requested for a Keystone Symposia conference entitled Cancer Vaccines organized by Drs. Llia Delamarre, Robert A. Seder and Nina Bhardwaj. The conference will be held in Vancouver, British Columbia from January 20-24, 2019. The success of immunotherapy in the treatment of cancer patients has proven the long-standing hypothesis that endogenous adaptive immune responses against the tumor can be harnessed to mediate protection by immune checkpoint blockade. This approach has shown impressive control of disease and improved survival in up to 50% of patients with certain tumors. Genetic and immune analysis of human cancers suggests that one mechanism of resistance to immune checkpoint blockade may be due to lack of tumor-specific T cells. In principle, vaccines have the potential to overcome this defect by either expanding low level existing tumor specific T cell responses or priming tumor specific T cells. Recent advances have improved our understanding of cancer neoantigens; these represent ideal targets to boost antitumor response via vaccination. In addition, current progress in this field has facilitated patient-specific vaccination strategies that are now in clinical development. These advances highlight the importance of vaccine delivery approaches that can induce potent and broad T cell immunity in an efficient manner for personalized therapy. This Keystone Symposia conference will highlight recent insights in the characterization of immunogenic cancer antigens, the biology and underlying mechanisms of T cell priming, and the development of novel approaches designed to expand T cell responses. Finally, a portion of this conference will also be devoted to the development of technologies to monitor T cell responses in response to immune interventions.